1. Field of the Invention
This invention relates to an image forming apparatus, such as a copying machine, which is adapted to manage opening/closing states of opening/closing portions such as for paper feed cassettes that can be to operated by a user at the time of use.
2. Related Art
Copying machines have been widespread nowadays as image forming apparatuses, many of which are so arranged that a user can select a desired size of paper to be copied to. Various systems for such a paper size selection have been developed.
One system is to use a plurality of pre-loaded paper feed cassettes, each accommodating paper of a different size, on a plurality of given slots, and to have a user select a paper size to be used through a control panel at the time of use. In this case, selectable paper sizes are unavoidably limited by the types of the pre-loaded paper feed cassettes. This system is suitable for relatively small copying machines.
Another system also enables selection of a paper feed cassette accommodating desired-size paper. In this system, along with the loading of such a paper feed cassette, information on the selected paper size can be manually inputted by keystroke through a control panel. In this case, two options are provided. One is to change (load) a type of paper feed cassette (i.e. paper size) first, and then to perform keystroke input as to the change of paper size through a control panel, and the other is to perform keystroke input first as to change of paper size through a control panel, and then to load a paper feed cassette which accommodates the desired-size paper on a predetermined loading position.
However, in the latter option of changing paper size, if there is a mismatch between an actually loaded paper feed cassette accommodating a certain size of paper and information on a paper size inputted by keystroke through a control panel, and copying is carried out in this state, paper jam may be caused.
One approach for preventing occurrences of such a mismatch is to prevent user's erroneous operation. In order to prevent this erroneous operation, the screen for setting change of paper size may be placed at a hierarchically deep position of a control panel screen avoiding a shallow position (easy-to-open hierarchy). In this way, user's careless or unintentional instructions on paper size may be decreased. This, however, may contrarily decrease operability for paper size change. Particularly, if an emphasis is to be put on the operability, a setting screen may have to be placed in a shallow hierarchy. Thus, prevention of erroneous operation and enhancement of operability have been in a contradictory relation with each other.
Of course, a copying machine may be permitted to have a mechanism in which, when a paper feed cassette has been changed to anther paper feed cassette of a desired paper size, the size of the paper cassette may be automatically detected. Disadvantageously, however, such a mechanism may involve structural complexity and induce increase of manufacturing costs.